thomas_dannhauser

True, but people will tend to hold their phone closer to their eye than they will a 21" monitor. People tend to adjust their viewing distance to a comfortable field of view (do you look at a billboard from 3 feet away?), so assuming the phone screen has sufficient resolution, they could see more detail than you would think. I agree that the smaller phone image may be more susceptible to the effects of ambient viewing conditions, and have inherently less impact than the larger image.

Sorry for the late reply here. When my Tamron 17-50 needed repairs (outside the warranty period), I sent it directly to Tamron. As I recall, they were pretty prompt about sending back an estimate upon receipt of the lens, and after I approved repairs, got the lens back to me in reasonable time. So I would start there... at worst you can decide not to proceed and have the lens sent back to you.

<p>Tom Yin,<br> To answer your question:<br> "...so basically what I'm trying to find out is the following: is it generally the case overseas that if you buy insurance then there is usually no hassle about small nicks when you return the car but if you don't buy insurance they get the money anyway by finding faults with it when you return it??"<br> My overseas travel has not been extensive enough that I have acquired sufficient experience and bravery to rent a car without insurance. Basically, I take the insurance to avoid last minute surprises, negotiations, and expenses. For instance, a car rental in South Africa that was driven in Kruger NP, partly on narrow dirt roads that resulted in "burnishing", rubs, scratches on the sides of the car from the adjacent shrubs and vegetation, and not a peep out of the rental company upon return of the car.</p>

<p>Same answer as Bob for domestic rentals -- my personal insurance covers my rentals, and so I never take the insurance option in this case. <br> But, overseas this is not the case, and for peace of mind I generally arrange for insurance when I make the reservation for the car on the internet rather than deal with this at the rental counter at the last minute. My lack of familiarity with local signage, driving habits and customs, and the car itself (right hand drive!) contribute to this. It roughly doubles the cost of a rental, but the additional charge relative to the overall cost of the trip is generally a small enough fraction that I just grit my teeth, hold my nose, and do it. So far.... no issues.</p>

<p>We stayed at a condominium in Yosemite West. Very pleasant and good price, but a bit of a drive from the main road (30 minutes?) at the time we were there (late fall), not including delays from roadwork at the time. You will need to eat elsewhere or cook for yourself at the condo; not sure what transportation options exist, other than your own car.</p>

<p>Would an external battery pack that you could keep under your clothes and connected via cable to your camera help with cold temperatures? Sorry -- don't have specifics, or even know if something compatible is available.</p>

<p>70-300L is generally accepted as the best presently available for this focal length combination. (Whether it represents the best value is another question.....) It is a relatively new lens, and so relatively fewer used copies are available, thus commands a higher used price. The 100-400L v1 competes with the v2 of the same lens, as well as some new 150-600 lenses from Tamron and Sigma that have very competitive optical performance and similar prices to the Canon. These additional choices, the numbers made during its long production run, plus its older technology cause the 100-400L v1 to command a lower price on the used market at present.<br> As others have suggested, there are many factors that should be considered in choosing a lens. Focal length is one of these, but size, weight, handling, optical characteristics, price all need to be considered.</p>

<p>+1 re: Glenn's comments about lenses for open or glass mounted slides. The former will require the slide to be heated sufficiently for the film to take on its final physical curvature. The optics of the Kodak lenses for open mount slides would then take this curvature into account. I think the Carousel projectors directed some of the heated air from the fan over the slides to precondition them to their projection curvature before actually being projected. Trying to adjust focus on a slide that had not yet "popped" would leave you struggling to adjust focus for the center or edge of the image. Similar focus problems arise trying to project open mount slides using a lens designed for glass mounted "flat" slides.<br> That is the one disadvantage of the stack loader.... you have to wait for each open-mount slide to "pop" into focus since the slides are not prewarmed as they are when in the tray. That can take a few seconds for each slide, but not having to load and unload the standard tray to quickly screen a new box of slides made it worth the wait. But waiting for each slide to adjust focus gets tedious for the viewer in a more formal slide show.<br> I think Navitar and Leica made nice projector lenses. </p>

<p>Haven't you forgotten to include the tripod head in your size estimates? (I agree with others who have recommended you lash the tripod to the exterior of your pack.)</p>

<p>Good polarizer filter for your 18-135 lens is a must-have, I think. Perhaps an extension tube or close-up filter if you think you might need closer-focusing capability than offered by your current lenses. Otherwise, you're set.<br> I've been to all these parks with nothing more than a 17-50, and think your current range would be suitable for 99% of the opportunities I would encounter. Personally, I would not have wanted to deal with the extra weight and bulk of yet another lens while hiking.</p>

<p>JDM -- thanks for your suggestion. I see KEH has some of the later versions of the Canon kit lens for ~$70-80, and I agree that may be the most economical solution. I think a few years ago the difference in optical quality between the Tamron 17-50 and one of the kit 18-55 lenses would be have so different that the extra cost to fix the Tamron would have been justified. Now... probably not.</p>

<p>Canon Rebel Xti with Tamron 17-50/2.8. I have recently been getting frequent Err99 codes accompanying lockup of the camera when this lens is attached; it has worked flawlessly for many years prior. I have cleaned contacts, shutdown and reset the camera, replaced batteries, etc., with no improvement. I do NOT have this problem when using another lens, so believe the problem is originating somewhere in my Tamron lens. I am considering sending the lens back to Tamron for repair. Has anyone else has had a similar experience, and did the repair fixed your Err99 problem? Thanks!</p>

<p>Iosif --<br> How were you lighting your acorn scene? That is, what was the primary light source? Also, you said your Nikon D90 no longer permits you to adjust ISO? Is the setting locked and you are compensating for different film speeds by adjusting shutter speed, aperture, lighting intensity? (As you can see, I am doing what all film engineers do and looking for something other than the film to blame for the result!)</p>

<p>I was a member of the Kodak R&D team for Ektachrome VS. I'm sure I have forgotten many of the details in the intervening years, but what I do remember is....<br> Yes, many people thought Velvia's speed rating of 50 was optimistic. I know we certainly thought so at Kodak, and generally considered it actually to have a speed of ISO40. Many photographers rated it that way; some even at ISO32. While other films were sometimes underexposed to enhance color (Kodachrome64 rated at ISO80, for instance), none of the photographers I interviewed ever did that with Velvia. In contrast, E100VS was often used at its ISO100 rating.<br> So, if you shot your Velvia at ISO50, it probably will look quite a bit darker than if you had shot 1/3 stop faster at ISO40. The change in density would be enhanced by Velvia's high contrast. Note in the characteristic curves that the aim maximum density of Velvia was 0.2-0.3 units higher than Ektachrome VS. The mid to upper scale contrast of Velvia is quite high to generate the increased density over the same approximate exposure range. So your wood background will get considerably darker as a result.<br> I also recall Velvia having a somewhat sharper toe contrast than the Ektachrome products. That would reduce the amount of highlight detail possible, but provided a "snap" to the image appearance. Landscape and nature photographers loved Velvia on cloudy days because of the high color saturation (especially greens), but also because its contrast characteristics enhanced the appearance of an image taken under low contrast lighting. Since many were shooting from a tripod, the low speed was not an issue.<br> The E100VS also enhanced colors, but emphasized reds and browns more. Good sharpness, and superb reciprocity failure characteristics... no color shifts as exposure times varied from 1/1000 second to seconds, even minutes. It was a bit grainier than the Velvia, but you were getting at least 1 stop extra speed, perhaps even more.<br> So, I think the darker results you are seeing from Velvia is probably due to the ISO50 speed you shot it at. Not sure if you have material or interest enough to repeat your experiment, but you might try it at ISO40 (or lower?) and see what you think of the results.<br> Thanks for your note.... it's nice to think about all this again.</p>

<p>I had a look at the NPS website to see where you are planning your hike. Lots of information there. Your hike certainly looks interesting, and there will be many fewer people than you would encounter on the Kaibab or Bright Angel trails. On the other hand, you will have to be entirely self-sufficient. Not sure what time of year you are planning your trip, but it sounds as if for much of the way down you will have no access to water other than what you are carrying. (You are right.... no mule service on this trail.) Sounds pretty ambitious if this is your first trip to Grand Canyon... what previous hiking experience do you have?<br> My wife and I hiked down to the campground near Phantom ranch a few years ago on the Bright Angel trail and then back up the next day. We arranged for our camping gear to be carried down by mule. Even that had bulk and weight limitations, and we had made arrangements for meals at Phantom Ranch so we didn't have to worry about food and cookgear. I was very happy not to have to carry any of this; even so my daypack certainly began to feel very heavy at the end of the day.<br> As others have suggested, your first priority should be water, shelter and food. Then, and only then, would I begin thinking about carrying photography gear. Anything taken should be carefully considered for weight and bulk. One of the signs we saw near a trailhead at the rim: "Hiking down -- optional. Climbing out -- mandatory!"<br> Its a unique and wonderful place. Have a great trip.</p>